The invention may include embodiments that relate to a composition for making an optical device structure, and to the article formed thereby. The invention may include embodiments that relate to a method of forming and/or using the optical device structure.
Modern high-speed communications systems may use polymer optical fibers for transmitting and receiving high-bandwidth data. The properties of polymer optical fibers with respect to flexibility, ease of handling and installation may drive their implementation in high bandwidth, short-haul data transmission applications such as fiber to the home, local area networks, and automotive information, diagnostic, and entertainment systems.
In some types of optical communication systems, there may be the need for interconnecting different discrete components. These components may include such polymer-based devices as lasers, detectors, fibers modulators, and switches. Polymer-based devices, such as waveguides, offer a viable way of interconnecting these components, and offer a potentially inexpensive interconnection scheme. Such polymer-based devices should be able to couple light vertically into or out of the waveguide with good efficiency and low propagation losses, which in turn may be determined primarily by the quality of both the polymer and the device boundary.
Opto-electronic multi-chip modules may be provided with an optical interconnect between the electronic circuitry and the “optical bench” portion of the package. One method to do this may have a vertical cavity surface-emitting laser (“VCSEL”) integrated with, and controlled by, the electronic portion of the module. The VCSEL may direct its laser light vertically into the base of the optical portion of the module. An approximate 45-degree angle “mirror” may be used to change the direction of the laser light from a vertical to a horizontal direction, thus directing it into the optical bench. This mirror may be difficult to fabricate with conventional methods for one or more reasons. The mirror should have a surface inclined by about 45 degrees with respect to the horizontal surface of the VCSEL. Furthermore, the mirror surface should be smooth to limit losses in light transmission, and it must be precisely aligned to the underlying VCSEL.
Previously, 45-degree angle mirrors have been defined either by laser ablation of the core polymer material at an appropriate angle, reactive ion etching using a gray scale mask, or embossing the required structure onto the polymer surface. Waveguide structures may be formed by several techniques including coating a lower cladding layer on a suitable substrate and forming a trench in the clad layer by embossing, etching or development, and filling the trench with a core material, and over-coating with a top clad layer. Ridge waveguides may be formed by coating a lower clad and core layer onto a substrate, patterning the core by etching or development to form a ridge, and over-coating with an upper clad layer. Planar waveguides may be formed by coating a lower clad and core material over a substrate, defining the waveguide by UV exposure and depositing an upper clad layer over it. Reactant diffusion may occur between the unexposed core and surrounding clad layers into the exposed core area to form a refractive index (RI) differential in the waveguide.
Polymer/epoxy blends with low epoxy content have been used to make low loss waveguides. Low epoxy content is less than 25 weight percent epoxy. A polymer/epoxy blend with a relatively higher index contrast between core and side-cladding layers may be required to couple light between two different (vertical) layers of waveguide structures while minimizing lateral light loss. This higher contrast may be accomplished with higher epoxy content. However, increasing the epoxy content increases scattering loss in the waveguide structures.
There continues to be a need for low loss radiation curable materials that may be used to make optical devices with control of at least one of topography, refractive index, or composition by a more direct process having fewer manufacturing steps. Furthermore, it may be desirable to develop a process that will enable the formation of optical device structures, such as waveguide structures, having a smooth, tapered edge to allow vertical interconnection with other optical devices or laser devices. Desired optical device structures may have optical properties such as low haze and a relatively high contrast in refractive index.